Due to the forgiveness that is extended to every Christian by their faith in Christ as pronounced in the New Testament, Luther argues, all Christians are free to act in any way they please. When they continue to behave according to God's law as it is written in the Bible, they do so of their own free will; acts of charity and kindness are nto something that is required in order to receive forgiveness, but rather is an outgrowth of the charity and kindness that exists in people's hearts regardless of the status of their salvation, which is already assured so long as their faith is pure and strong. This quite obviously limits the power of the Church as far as condemning acts of any kind is concerned; even one found guilty of heresy would, according to Luther's argument, still receive salvation through their faith in Jesus Christ as the savior of all mankind, who died to redeem man's sins. The argument as Luther lays it out in this treatise is, of course, far more complex than this above summary implies. He distinguishes the two natures of man as being spiritual and bodily. The spirit or soul of man, Luther goes on to insist, is neither harmed by nor gains benefit from anything that affects the body of man. Sacred offices and vestments mean as little to a man's soul as riches and luxury -- they means absolutely nothing, as a matter of fact. It is only faith that has an effect on the soul, Luther argues, and in fact other Christian virtues can be seen as extensions of faith and not separate means to gaining the rewards of salvation and justification that faith provides. This is largely the crux of Luther's argument, explaining why faith is necessary and actions are meaningless to those that would seek salvation in the Christian perspective.

Luther's argument grows more complex when h turns...

As a reputation for truth and righteousness is considered to be the highest reputation once can achieve, according to Luther, the soul of man automatically sees God as a true and righteous being. As such, his laws and promises are also true and righteous, and thus to earn a reputation of truth and righteousness for himself man must, though only for bodily rewards having nothing to do with the soul, behave according to this law himself. These elements -- that of salvation through faith alone and of righteous behavior being a freely made choice brought about by the inherent righteousness of God and of a good man's soul -- are the simple and central tenets of Luther's treatise. There are other theological underpinnings he uses to shore up these arguments, including quoting the New Testament idea that good or evil men might be "recognized" by their works, but going on to insist that these works have no bearing on their ultimate salvation.
Conclusion

In the context provided by the letter to Pope Leo X, it becomes clear that an undercurrent in Martin Luther's On the Freedom of a Christian is the erosion of the Church's power from underneath. By claiming that faith and faith alone can lead to salvation, and that the trappings of an office are by no means a sign of righteousness or a means of achieving salvation. This would mean that the Church holds no real power in this physical world, and exists solely to bring the word of God to the rest of mankind. This is certainly one of the main tenets of Luther's overall philosophy, and is strongly supported in this treatise.